The induction of an immune response is a multistep process involving cascading interactions between lymphocyte, macrophages, and their cytokines. The requirements for activation of resting cells appear more complex than for activation of nonresting (partially activated) cells. Early versus late requirements potentially can be resolved by examining the distinctions in activation requirements of resting versus nonresting cells. Early events in activation include the expression of interleukin receptors and apparently of the aGml glycolipid. It is not known how early expression of aGml occurs. The objective of the current study is to examine the kinetics appearance of aGml during activation of aGml negative cells purified by cell sorting and to compare the requirements for activation of aGml- positive and negative T lymphocytes purified by flow cytometric sorting from normal murine lymphoid tissue. Since the requirements for activation of some T cell subsets (CD 4+) appear to be more stringent than those of other subsets (CD 8+) and since distinct requirements may exist for early versus late steps in activation, the activation requirements will be examined separately for the aGml fractions of CD 4+ cells and CD 8+ cells and for the induction of lymphokine responsiveness, production of lymphokines, and expression of cytolytic activity. The study will provide substantial information on the requirements for attainment of comparable levels of activation in CD 4+ versus CD 8+ cells and will allow a resolution of whether CD 4+ or CD 8+ T lymphocytes which express aGml in vivo display a heightened level of activation and/or less stringent requirements for activation than the T lymphocytes which do not express aGml.